The present invention concerns a tool head unit with a machine tool spindle or, respectively a milling or cutting head unit with a motor cutting head spindle and a machine or, respectively, a milling machine with such a tool spindle unit.
In a post-published patent application with the docket No. 10 2005 043 835.0 filed 13 Sep. 2005 a portal milling machine is described which includes a portal supported on side supports and a machine table firmly anchored to a foundation. The portal is movable in a horizontal X-direction and carries a vertically arranged arm which is movable in a horizontal Y-direction which is normal to the X-direction. The arm carries a support beam which is movable in a vertical Z-direction and carries a milling head with a motor milling spindle.
The milling head includes a fork which, by a torque motor, is rotatable about C-axis coinciding with the Z-axis. The spindle housing of a milling spindle is on two fork arms so as to be pivotable about an A-axis extending normal to the C-axis. A further torque motor is provided as drive for the pivoting of the spindle housing about the A-axis. The milling spindle includes a cutting tool which is driven by a motor and which projects outwardly from the spindle housing for performing during operation a cutting procedure on a workpiece placed onto the machine table.
The milling machine is intended for the manufacture of tools, molds and models or for the manufacture in the automobile—air and space travel industries and is suitable to work very large and complicated 3-dimensional components which may have very fine surface details. It permits the execution complicated 5-axis simultaneous operations with high precision in a relatively short period.
However there are certain disadvantages associated with this type of milling heads which use a combination of a for example vertical axis of rotation C and a for example horizontal pivot axis A which extends normally thereto. During the positioning of the milling tool into the angular position which is required for the machining of the workpiece a rotation of the milling tool by a substantial angle about the C axis may be necessary if it happens to be in an unfavorable angular position about the A-axis. This is particularly true, if its rotation about the C-axis is limited to about +/−180° with respect to a predetermined zero position because of the guide arrangement for the cables required for the energy supply and the signal transmission. In an extreme case a back-rotation about the C-axis by almost a full turn may become necessary for only a small position change. As a result the operating speed is substantially reduced. It would of course also be possible to use slide contact rings for the transmission of the energy and the signals but this would substantially increase the costs of a milling head.
Furthermore, with the use of a milling head with A- and C-axes an electronic orientation error compensation is not possible or is possible only with very high expenditures. Therefore all components of the milling head and of the milling machine must be manufactured and operate with high precision in order to obtain the required quality.
WO 00/25976 A2 discloses a joint tool head based on the principle of rod kinematics. It includes a tool platform which is movable along three axes, at least three guide arms which are linked to the tool platform and are movable independently of one another in parallel, and at least three linear drives arranged in spaced relationship around the tool platform for operating the guide arms linked thereto. The links are linked to the tool platform so as to be movable in any direction and to the linear movement drives so as to be pivotable about axis extending normal to the direction of movement of the linear movement drives. At the tool platform a motor spindle may be arranged in such a way that it is movable about two pivot axis and along a linear axis. Because of the support arrangement of the tool platform the motor spindle can rapidly be brought unto any required position within the measuring space. However, because of a highly limited length of the linear axis and a pivot angle limited to about +/−40° the measuring space is relatively small so that the application area is limited. Large 3D-parts as they are used for example in connection with model form and die tool construction can hardly be manufactured.
DE 198 50 603 A1 discloses a milling head unit with a cardanic joint support structure for a milling spindle. The milling head unit includes a support housing which is mounted to a spindle beam which is movable in X-, Y-, and Z directions and a pivot housing which is accommodated in the support housing so as to be pivotable about a first axis B. The pivot movement about the axis B is caused by torque motors which are flanged at both sides to the support housing and which directly drive the pivot housing. In the pivot housing a spindle accommodation housing is arranged so as to be pivotable about a horizontal axis A and is pivoted by torque motors arranged at opposite sides. The spindle accommodation housing carries a motor milling spindle with a direct drive for a milling tool. With the pivot axes A, B of the milling head unit which extend normally to one another and not parallel to the Z-axis, the milling spindle can be pivoted directly and rapidly into any required work position. Pivoting about a C-axis coinciding with the Z-axis is not necessary. As a result, with this kind of milling head unit with A- and B-pivot axes an electronic orientation error compensation is possible.
The cardanic support as it is proposed in DE 198 50 603 A1 however requires a relatively large construction space. Each housing is essentially box-like, so as to accommodate therein another housing, together with a drive shaft therefor. As a result also the pivot angle about the pivot axis A, B is very much limited.
Based on this state of the art it is the object of the present invention to overcome the above disadvantages and, respectively shortcomings. It is particularly an object of the present invention to provide a dynamic tool head unit suitable for tool and die and model construction, which is of relatively compact design and provides for relatively large pivot angles. Preferably the arrangement of the tool head unit should facilitate an electronic orientation error compensation.
Another object of the present invention is to provide a machine tool with such a tool head unit by which also large 3 D-components can be manufactured with a high operating speed.
These and other objects of the present invention are solved by the tool head unit according to the invention.